Ball joints allow pivoting movement of automotive suspension or steering components relative to each other while retaining the capacity to transmit axial and shear forces thereby accommodating wheel movement, steering movement, stability and wheel alignment.
Ball joints typically include a stud with a shank that is threaded at one end for releasably connecting to an adjacent component. Other means of connecting the stud and component are also used. The stud has a spherical ball at the opposite end mounted within spherical bearings or retainer ring housed in a ball joint housing. The ball stud is retained in the ball joint housing extending through a central opening in the directional bearing or retainer ring.
To accommodate an asymmetric range of motion in some components, the swing angle of the ball stud relative to the housing axis is not uniform in all directions in directional ball joints but is asymmetric with a swing angle that varies and must be accommodated by an elliptical opening in the bearing or retainer ring to allow free movement of the ball stud. Directional bearings include a spherical interior surface and allow a greater swing angle in predetermined directions. The central opening of the directional bearing is wider and narrower to allow the longitudinal stud axis to move freely within a major swing plane through the housing axis in a range of ±angle α relative to the housing axis and a minor swing plane through the housing axis in a range of ±angle β relative to the housing axis, where α is greater than β. An example is described in U.S. Pat. No. 8,851,785 which includes a retainer ring with an elliptical opening having major and minor axes.
It is critical to align the major and minor swing plane of the directional ball joint with the correct planes of motion through which an associated automotive component moves. Misalignment results in the restriction of the ball stud motion by interference with the edges of the opening through which the ball stud projects. Failure of the ball stud or bearing can result from such interference.
Correct alignment of the ball joint major and minor swing planes with the associated automotive component into which it is installed is controlled through proper training during manufacture and instructions to mechanics in the installation information provided. However errors can occur and incorrect alignment can result in catastrophic failure of ball studs in automotive suspension, stabilization, and steering systems.
Features that distinguish the present invention from the background art will be apparent from review of the disclosure, drawings and description of the invention presented below.